It has been hypothesized that susceptible individuals develop symptoms of Tourette's Syndrome (TS), Obsessive Compulsive Disorder (OCD) and Attention Deficit Hyperactivity Disorder (ADHD) as a result of post-infectious autoimmune processes. The long term goal of this project is to establish whether or not immunologicl alterations in the periphery accompany an increase in clinical severity in pediatic patients with TS, OCD, and ADHD.